The present invention relates to a micelle dispersion and a process for producing the micelle dispersion, and more particularly to a micelle dispersion which can provide a color filter in an excellent yield without color overlapping and a process for producing the micelle dispersion.
As the process for producing organic thin films comprising coloring materials and the like, the vacuum deposition process, the heat CVD (Chemical Vapor Deposition) process, the plasma CVD process, the ultra-high vacuum (the ion beam and molecular beam epitaxy) process, the LB (Langmuir-Blodgett) film process and the casting process have heretofore been used.
However, these processes have a problem in that thin films cannot be formed when a material for the thin films such as a coloring material has poor heat resistance or is insoluble in organic solvents because operations such as heating the material and dissolving the material in an organic solvent are required.
Recently, a process for producing a thin film by an electrolytic treatment has been proposed (Japanese Patent Application Laid-Open No. Showa 63(1988)-243298). In this process, a micelle dispersion is prepared by dispersing hydrophobic particles such as particles of coloring materials in an aqueous medium containing a dispersant and a thin film is formed on an electrode by an electrolytic treatment of the prepared micelle dispersion. Thin films can be easily prepared from materials having poor heat resistance or poor solubility in an aqueous medium in accordance with this process. Therefore, it has been attempted that color filters are produced in accordance with the above process comprising the electrolytic treatment (Japanese Patent Application (as a national phase under PCT) Laid-Open No. Showa 63(1988)-505384 and Japanese Patent Application Laid-Open No. Heisei 3(1991)-102302).
In the above process comprising the electrolytic treatment, the equilibrium concentration of a dispersant in a dispersion significantly affects the formation of thin films. For example, when the equilibrium concentration is very small, problems arise in that particles aggregate together during production of a dispersion to cause poor dispersion and that substrates are stained due to formation of rough pixels during formation of thin films and the spectroscopic property deteriorates. When the equilibrium concentration is very great, problems arise in that thin films are not formed occasionally in the film formation process even when an electric current is applied, that thin films are not formed in peripheral portions of pixels to cause formation of blank portions and that films are not formed uniformly in peripheral portions of a substrate. Therefore, reproducible production of thin films is possible only when the equilibrium concentration of hydrophobic particles in a dispersion is rigorously controlled.
In Japanese Patent Application Laid-Open No. Heisei 10(1988)310898, a process which comprises dipping a conductive substrate into a micelle dispersion containing a hydrophobic substance and a surfactant of a ferrocene derivative dispersed in an aqueous medium and producing a thin film of the hydrophobic substance while the fraction of an oxidized compound in the surfactant of a ferrocene derivative is kept in the range of 0 to 0.3, is described. However, when the above micelle dispersion is used for producing a color filter having thin films of three primary colors of R (red), G (green) and B (blue) and an electric current is passed successively through portions for forming the thin films of three primary colors, the problem of color overlapping such as green color laid over red color arises.
The present invention, has been made to overcome the above problems and has an object of providing a micelle dispersion which does not cause color overlapping in the production of a color filter by the electrolytic treatment and a process for producing the micelle dispersion.
As the result of intensive studies by the present inventors to achieve the above object, it was found that the object can be achieved by adjusting the concentrations of an oxidized compound and a reduced compound of a surfactant in the micelle dispersion within specific ranges. The present invention has been completed based on this knowledge.
The present invention provides a micelle dispersion which comprises hydrophobic particles, conductive particles and a surfactant of a ferrocene derivative dispersed in an aqueous medium, wherein the surfactant of a ferrocene derivative in an equilibrium concentration comprises an oxidized compound in a concentration of 40 xcexcg/ml or less and a reduced compound in a concentration of 50 to 300 xcexcg/ml.
The present invention also provides a process for producing a micelle dispersion which comprises dispersing hydrophobic particles, conductive particles and a surfactant of a ferrocene derivative in an aqueous medium, wherein an oxidized compound in the surfactant of a ferrocene derivative is removed with at least one of an ion exchange resin and a reducing agent.
In particular, in accordance with the above process, a micelle dispersion comprising an oxidized compound in a concentration of 40 xcexcg/ml or less and a reduced compound in a concentration of 50 to 300 xcexcg/ml can be obtained by removing the oxidized compound in the surfactant of a ferrocene derivative with at least one of an ion exchange resin and a reducing agent.